going out on a limb, i guess these people would say that they don't know much category theory because they understand that category theory contains results, not just definitions. moreover, it bleeds into algebra, geometry, k-theory, etc. pretty fast. even some /very/ respectable mathematicians (e.g. matsumura) are hesitant to say they know much about all of these things.
i think it's really cool that haskell makes programmers interested in math. i'm still pretty sure that everything about it that has anything to do with category theory is contained in the Prelude or on hackage, tho. in other words, all the category theory stuff that's "built-in" to haskell is itself expressed in haskell. at the risk of raising some hairs: at one point Crockford mentioned that making monads is possible in javascript, too.
To be clear, I would guess (and I'm by no means sure) that these very highly regarded Haskellers barely know how to define "category" and "functor" (the mathematical versions, not the Haskell versions) and certainly don't know how to define "natural transformation". I admit the following as evidence: https://twitter.com/bos31337/status/656319244263518208
I think it's very important that we, as the Haskell community, reaffirm at every possible opportunity that you do not need to know category theory, or even much mathematics, to succeed at Haskell.
he wrote my window manager!
going out on a limb, i guess these people would say that they don't know much category theory because they understand that category theory contains results, not just definitions. moreover, it bleeds into algebra, geometry, k-theory, etc. pretty fast. even some /very/ respectable mathematicians (e.g. matsumura) are hesitant to say they know much about all of these things.
i think it's really cool that haskell makes programmers interested in math. i'm still pretty sure that everything about it that has anything to do with category theory is contained in the Prelude or on hackage, tho. in other words, all the category theory stuff that's "built-in" to haskell is itself expressed in haskell. at the risk of raising some hairs: at one point Crockford mentioned that making monads is possible in javascript, too.